Various types of security systems have been proposed which utilize sensors and triggers to control access to a protected area, such as by way of a door or a window to premises or a building. Additionally, sensors are utilized for controlling actuation of an ignition system on an automobile or other vehicle. Typically, to allow access through doors or other access points, devices which release or position locking elements, such as solenoid switches, are typically employed. Such sensors and trigger switches operate upon a predetermined voltage value to operate an electromechanical device to gain access to the premises. In order to actuate an automobile's ignition system, a predetermined voltage value is sensed by a microprocessor associated with the ignition system in order to operate the vehicle.
Conventional security systems although providing a reasonable measure of protection, can be defeated by an unauthorized person to gain entry to a secured premises or to steal a vehicle. By simulating the required output voltage value of the security sensor, the thief can in effect bypass the sensor and defeat the security system. In this manner, a key for operation of the vehicle ignition lock would not be necessary in order to activate the automobile's ignition system. Similarly, security cards or keys would be unnecessary to gain entry to a premises if the predetermined voltage levels necessary to operate electromechanical locks were determinable.
Since many improved security systems utilize programmable voltage sources which are operable upon sensing a predetermined condition such as, for example, the operation of a vehicle ignition lock or door lock, in order to prevent such security systems from being defeated, a need has arisen for a system for preventing detection of the predetermined voltage values which operate the security system. In systems were multiple sensors are utilized, in security systems and elsewhere, it is also desirable to identify which one of the multiple sensors has been activated where a common output signal line is utilized for connecting the multiple sensors.